There are many scenarios in which it is desirable to determine a direction (angle) of arrival of a radio signal at a location where the radio signal is detected. For example, there are surveillance applications where it is desirable to identify an approximate location of a transmitter that is transmitting radio signals over a frequency of interest. In another example, it is often desirable to relatively accurately ascertain, with respect to a particular location, an angle of arrival of television signals, such that an antenna can be properly directed to achieve maximum signal-to-noise ratio (SNR) of a received television signal. Still further, if it is desired to establish a two-way radio link between two base stations, angles of arrival of radio signals between the base stations can be used to direct transmissions between the base stations (e.g., through beamforming techniques).
Conventional techniques for determining angle of arrival are expensive, labor-intensive, and/or aesthetically displeasing. For example, an antenna may be mounted on a rotatable mount, and the mount can be rotated to identify a position where the antenna receives the signal with highest SNR. This technique involves the expense of the rotatable mount, and is also known to be somewhat inaccurate. Another exemplary technique involves mounting an array of ¼ wavelength antennas on a ground plane, where the ground plane is arranged horizontally and the antennas of the array vertically extend from the ground plane. This technique requires free airspace between antennas of the array—thus, the array and ground plane is difficult to conceal, rendering such system aesthetically displeasing.